Electrolytic bridge assembly for



5 Sheets-Sheet 1 A Trae/VH March 24, 1964 M. HUTcHlsoN ETAL ELECTROLYTIC BRIDGE ASSEMBLY FOR THE ANoDIc PAssIvATIoN oF METALS Filed march s. 1959 ias/4 March 24, 1964 M. HUTcHlsoN ETAL 3,125,328

ELECTROLYTIC BRIDGE ASSEMBLY FOR THE ANODIC PASSIVATION OF METALS Filed March 9, 1959 5 Sheets-Sheet 2 INVENTORS.

Mc-QLE HurcHlso/v, OLE/u L. Pleas Jef BY JOHN D@ SUUBUQY ggf; @M4

ATTOP/UEY March 24, 1964 M. HuTcHlsoN ETAL. 3,126,328

ELECTROLYTIC BRIDGE ASSEMBLY FOR THE NODIC PASSIVATION OF METALS 3. Sheets-Sheet 3 Filed March 9. 1959 INVENTORS. Mem.: HurcHlsoN, OLeN L. Qfqqs .Jeff dol-1M D. Suoauer 522%?! M United States Patent O 3,126,328 ELECTROLYHC BRHDGE ASSEMBLY FUR THE ANDIC PASSHVATION F METALS Merle Hutchison, (bien L. Riggs, Jr., and J ohn D. Sudbury,

Ponca City, Gitta., assignors to Continental Oil Conipany, Ponca City, Ghia., a corporation of Delaware Filed Mar. 9, 1959, Ser. No. '797,986 l Claim. (Cl. 21M-196) This invention relates generally to an improved system of anodic passivation for minimizing corrosion of vessels containing corrosive solutions, and more particularly, but not by way of limitation, to a novel electrolytic bridge assembly for such systems. This is a continuation-inpart of applicants co-pending application, entitled Anodic Protection Against Corrosion, tiled December 1, 1958, Serial No. 777,499, now abandoned.

The above-mentioned co-pending application discloses a system for anodically passivating a vessel containing a corrosive solution, wherein an anodic current is passed through the solution between the walls of the vessel and an electrode supported in the solution. The amount of anodic current is controlled in accordance with the potential difference between the vessel and a standard electrode communicating electro-chemically with the solution in the vessel. The corrosive solutions frequently encountered are harmful to most standard electrodes, and assurance must be had that the standard electrode does not contaminate the corrosive solution. Therefore, the standard electrode is desirably contained out of contact with the corrosive solution and is connected electrochemically with the solution by means of an electrolytic bridge. However, the electrolyte in the bridge must make positive contact with both the standard electrode and the solution under all operating conditions, such as during varying levels of the corrosive solution in the vessel being protected and during rather violent agitation of the corrosive solution. Also, as a practical matter, the electrolytic bridge must be operative for extended periods of time, without frequent attention by an operator of the process utilizing the vessel being protected.

The present invention contemplates a novel salt or electrolytic bridge assembly employing a reservoir of a suitable electrolyte positioned remote from the corrosive solution in intimate contact with a standard electrode. The electrolyte is connected to the corrosive solution through a tubular member extending into the corrosive solution to provide an electrical connection between the standard electrode and the corrosive solution. The electrolyte is gradually dripped from the tubular member into the corrosive solution to assure that a fresh supply of the electrolyte will be constantly available for making sutiicient electrical contact with the corrosive solution, yet an insuiiicient amount of electrolyte is discharged into the corrosive solution to interfere with the process employing the corrosive solution. An excess of salt is retained in the reservoir in such a position as not to interfere with the function of the electrolytic bridge, yet retains the electrolyte at the desired concentration and facilitates the replenishing of the active electrolyte by the simple addition of water to the reservoir. The tubular member containing the electrolyte is protected within the Vessel containing the corrosive solution against violent agitation of the corrosive solution, or other actions, to assure that the electrolyte will not be dumped or injected in a large quantity into the corrosive solution.

An important object of this invention is to provide an eiiicient system for minimizing corroson of vessels by anodic passivation.

Another object of this invention is to provide an electrolytic bridge between the standard electrode and a 3,i2b,328 Patented Mar. 24, 1964 ice corrosive solution in a vessel being protected by anodic passivation which will require a minimum of attention by an operator and which will provide an etiicient electrical connection between the standard electrode and the corrosive solution under all operating conditions.

A further object of this invention is to provide an electrolytic bridge between a standard electrode and a corrosive solution contained within a vessel, without the setting up of secondary cells between the vessel and the bridge, or the supporting structure of the bridge, which would foul the monitoring of the potential difference between the standard electrode and the vessel.

Another object of this invention is to minimize deterioration of a standard electrode in an anodic passivation system, and to prevent dilution of the corrosive solution in a vessel being protected, while maintaining an eilicient electrical connection between the corrosive solution and the standard electrode.

A still further object of this invention is to provide a system and electrolytic bridge assembly for the anodic passivation of metals which is simple in construction, which may be economically manufactured, and which will have a long service life.

Other objects and advantages of the invention will be evident from the following detailed description, when read in conjunction with the accompanying drawings which illustrate our invention.

In the drawings:

FIGURE l is a schematic illustration of a system constructed in accordance with this invention.

FIGURE 2 is a vertical sectional View through a preferred electrolytic bridge assembly.

FlGURE 3 is a vertical sectional view through a modied lelectrolytic bridge assembly incorporating this in- Vention.

FIGURE 4 is a vertical sectional view through still another rnoditied electrolytic bridge assembly incorporating this invention.

FIGURE 5 is a sectional view as taken along lines 5 5 of FIG. 4.

Referring to the drawings in detail, and particularly FlG. l, reference character liti designates a vessel containing a corrosive solution 12 and which is to be protected by a system constructed in accordance with the present invention. The corrosive solution l2 is electrolytic and may be either acidic or alkaline. A source lit of direct current energy is connected to the vessel l@ and to an electrode 16 positioned in the solution l2 to pass an anodic current through the solution l2 and passivate the exposed inner surfaces of the vessel lti against the corrosive action of the solution l2.

The anodic current is controlled by any suitable type of controller 18 connected to` the energy source 14 in any suitable manner, such as by means of a switch 20 interposed in the conductor 22 leading from the source 14 to the electrode i6. A type of controller i8 which may be used is shown in detail in the above-mentioned co-pending application. The controller Ls is connected across the vessel l@ and a standard electrode 24 communicating with the solution l2 as will be hereinafter described, to monitor the potential dicerence between the vessel liti and the standard electrode 214. Thus, for an eiiicient operation of the controller 18, the standard electrode 24 must communicate electrically with the solution l2 under all operating conditions, such as during variation in the level of the solution l2 in the vessel l@ and during rather violent agitation of the solution l2, such as occurs in many processes utilizing corrosive solutions. lt should also be noted at this point that the standard electrode 2.4 may take any desired form, such as a calomel electrode,

a copper-copper sulphate electrode, a silversilver chloride electrode or a hydrogen electrode.

A preferred electrolytic bridge assembly for connecting the standard electrode 24 to the solution 12 is illustrated in detail in FIG. 2 and is designated generally by reference character 26. The assembly 26 comprises a reservoir 28 preferably having an air vent 30 in the upper end thereof and a tapered bottom wall 32. The reservoir 23 is supported above the level of the solution 12, as by supports 33 (see FIG. 1) extending upwardly from the top of the vessel 1t). The desired electrolyte 34, such as KCl, is stored in the reservoir 28 at a level sufficient to contact a standard electrode 24 suspended from the top wall of the reservoir 26. The standard electrode 24 illustrated in FIG. 2 is a calomel electrode.

A conduit 36 extends through the central portion of the bottom wall 32 of the reservoir 28 and then extends an appreciable distance up into the reservoir 28 above the bottom wall 32 for purposes which will be hereinafter described. A suitable sealing ring 37 is preferably provided in the bottom wall 32 around the conduit 36. The upper end portion 38 of the conduit 36 is preferably extended adjacent one side of the reservoir 28 in spaced relation with respect to the electrode 24 to assure that the electrode 24 will not contact the conduit 36 when the electrode is replaced with a new electrode in a reservoir 28. The conduit 36 extends generally downward toward the vessel and is suitably connected to a weeping glass bridge 40 of any suitable type which has a restricted outlet or tip 42 at the lower end thereof. The weeping glass bridge 40 may be secured at any desired point in the vessel 10, the only requirement being that the weeping glass bridge 46 be supported in a generally vertical position with the lower end 42 thereof immersed in the solution 12.

When the vessel 10 is provided with an internally threaded coupling 44, as shown in FIG. 2, the weeping glass bridge 40 may be inserted through this coupling. A tubular head 46 is telescoped over the upper portion of the weeping glass bridge 46 and is threadedly connected to the coupling 44, as well as being connected by threads 48 to mating threads on the upper end portion of the bridge 40. Also, a suitable sealing ring 50 may be provided between the weeping glass bridge 40 and the upper end portion of the tubular head 46 to prevent any possibility of corrosive solution leaking through the tubular head 46 during operation of the present system. It may also be noted that the extreme upper end 52 of the weeping glass bridge 40 is preferably threadedly connected to the lower end of the conduit 36 and sealed thereto by an O-ring 54 to further assure that no leakage of either the electrolyte 34 or the solution 12 will occur.

A high strength tubular member 56 is either formed on the lower end of the tubular head 46 or rigidly secured to the lower end of the head 46 and extends downwardly around the weeping glass bridge 40 to a point adjacent the tip 42 on the lower end of the bridge. This tubular member 56 protects the weeping glass bridge 4t) against breakage by such actions as violent agitation of the corrosive solution 12. Also, the tubular member 56 and the tubular head 46 must be constructed out of either a material inert to the environment or the same material as the vessel 10 to prevent the formation of a secondary cell with the corrosive solution 12 which would interfere with the operation of the controller 18 and prevent a precise control of the anodic current. A sealing ring 58 is preferably secured in the lower end portion of the tubular member 56 to extend around the weeping glass bridge 40 a short distance above the tip 42 and prevent any possible upward flow of the corrosive solution through the tubular member 56 and tubular head 46. The extreme lower end portion 60 of the tubular member 56 is preferably provided with slots or openings 62 and is extended downwardly a short distance beyond the lower end 4Z of the bridge 40 to protect the lower end of the bridge while allowing substantially free circulation of the corrosive solution 12 in contact with the lower end of the bridge.

In operation of the electrolytic bridge assembly 26, the reservoir 23 is filled with the electrolyte 34 up to a level where the electrolyte encloses at least the major portion of the active end portion of the electrode 24- to assure intimate Contact of the electrode 24 with the electrolyte. It will also be apparent that the electrolyte 34 will flow downwardly into the conduit 36 and ll both the conduit 36 and the weeping glass bridge 40. It is also preferred to deposit an excess of salt 64 in the lower portion of the reservoir 28 below the upper end of the conduit 36 to assure that the electrolyte 34 will remain saturated and provide an eicient transmission of current. The excess salt 64 also facilitates replenishing the electrolyte 34, since the electrolyte may be replenished by adding a small quantity of water to the reservoir 28.

The electrolyte 34 gradually drips from the tip 42 of the weeping glass bridge 40 into the solution 12 in the Vessel 10. This gradual leakage or dripping of the electrolyte from the weeping glass bridge 40 assures that a fresh supply of the electrolyte will be constantly available at the lower end of the bridge for contact with the corrosive solution to provide an eicicnt junction between the electrolyte and the solution 12. However, the amount of electrolyte dripped through the tip 42 may be substantially negligible insofar as dilution of solution 12 is concerned. For example, when using a weeping glass bridge and when using KCl as the electrolyte, electrolyte will drip from the lower end of the bridge at the rate of 0.002 to 0.05 ml. per hour. It will thus be apparent that an insufficient amount of electrolyte will be mixed with the corrosive solution 12 to provide any measurable contamination of the corrosive solution 12, and that the supply of electrolyte 34 will remain available to provide electrical communication between the solution 12 and the standard electrode 24 for an extended period of time without requiring the attention of the operator of the system.

A modified electrolytic bridge assembly for use with a vessel having a hanged opening is illustrated in detail in FIG. 3 and is generally designated by reference character 66. The assembly 66 comprises areservoir 63 constructed in substantially the same manner as the reservoir 28 previously described in having a tapered bottom wall 70 and containing the standard electrode 24. In this embodiment of the invention, a conduit 72 is connected with the side of the reservoir 68 a short distance above the bottom wall 70 and then extends generally downwardly from the reservoir 68 toward the vessel 10. The lower end 74 of the conduit 72 is suitably connected to the upper end of a weeping glass bridge 4t). In this assembly, the weeping glass bridge 40 is enclosed by a tubular member 76 having a flange 78 adjacent the upper end thereof for connection with a mating ange (not shown) on the vessel 10. Suitable caps 80 are threadedly secured on the upper and lower ends of the tubular member 76 to retain packing 82 around the upper and lower end portions of the weeping glass bridge 40. The tip 42 of the weeping glass bridge 40 protrudes below the lower cap 82 and is protected by a Wirelike guard 84 secured to the lower end of the lower cap 80. The wire guard 84 protects the tip 42 against accidental damage and yet permits a free circulation of the corrosive solution 12 in contact with the tip 42.

The weeping glass bridge 40 shown in FIG. 2 is of a length to extend downwardly in the vessel 10 to position the tip 42 thereof in the corrosive solution 12, even though the level of the solution 12 may vary during operation of the system. It will therefore be apparent that the lower end of the weeping glass bridge 40 should be positioned in proximity with the bottom of the vessel 10. The tubular member '76 extends around the weeping glass bridge 40 from the flange 78 downwardly into proximity with the tip 42 to assure that the bridge 40 will not be broken by violent agitation of the solution 12 or by an inadvertent blow. It should again be observed that the tubular member 76, flange 78, and caps 80 should be constructed out of either an inert material or the same material as the vessel to prevent the formation of a secondary cell in the vessel 10.

The bridge assembly 66 operates in substantially the same manner as the bridge assembly 27 previously described, in that the electrolyte 34 surrounds the electrode 24 and extends downwardly through the conduit 74 and the weeping glass bridge 40. As the electrolyte gradually drips from the tip 42 of the weeping glass bridge 4t), a fresh supply of the electrolyte is constantly available for making an eicient junction with the solution 12 and providing a sufficient transfer of current through the electrolyte to the standard electrode 24. Also, an excess 64 of the salt of the electrolyte 34 is preferably provided in the lower end portion of the reservoir 68 below the connection of the conduit 72 with the reservoir to assure that the electrolyte will remain concentrated and to facilitate replenishment of the electrolyte. The packing 82 at the upper and lower end portions of the weeping glass bridge 40 will assure that no portion of the corrosive solution 12 will leak from the vessel 10 and will assure that no electrolyte will be leaked out of the system, except into the corrosive solution 12.

A still further modified electrolytic bridge assembly, particularly adapted for use in vessels wherein the level of the corrosive solution varies, is illustrated in detail in FIGS. 4 and 5 and is generally designated by reference character 86. The assembly 86 comprises a frame 8S rigidly secured in the vessel 10 and extending from the top to the bottom of the vessel. The frame 8S has two opposed side members 90 which are preferably T-shaped in cross-section as illustrated in FIG. 5. The lower ends of the members 90 may be interconnected and braced by another T-shaped member 92 if desired. A tubular head 94 is slidingly secured in the frame 88 for vertical movement upon a change in the level of the corrosive solution 12 contained in the vessel 10. Grooves 96 are formed in the opposite sides of the head 94, as illustrated in FIG. 5, to receive the inwardly extending portion of each of the frame members 90, such that the head 94 will be secured in the vessel 10 against a turning movement or a sideways movement, but will be allowed to slide vertically on the frame 83. A weeping glass bridge 40 is secured in the tubular head 94 by cooperating threads 98, and the upper end of the bridge 46 is preferably sealed in the head 94 by a suitable sealing ring 100.

A tubular extension 192 is formed on the lower end of the head 94 and extends downwardly around the bridge 40 into proximity with the lower end or tip 42 of the bridge. A suitable sealing ring 1614 is secured in the extension 102 around the bridge 4t) to prevent an upward flow of the corrosive solution 12 through the extension 102 and head 94. Also, openings 1636 are formed in the extreme lower end portion of the extension 102 around the tip 42 to permit circulation of the solution 12 around the tip 42 in the same manner as previously described in connection with FIG. 2.

The extreme upper end 108 of the weeping glass bridge 4t) is threadedly secured to the lower end of a conduit 110 extending vertically through the top of the vessel 10. Also, a sealing ring 112 is preferably provided in the lower end of the conduit 110 to seal against the upper end of the bridge 40 and prevent a leakage of electrolyte from the lower end of the conduit 110. The conduit 116 may be of any suitable construction, such as plastic, and is suitably connected to an electrolyte reservoir, such as the type shown in FIGS. 2 or 3. A supply of electrolyte is provided in the conduit 110 in communication with a standard electrode in the same manner as previously described in connection with FIGS. 2 and 3. A high strength tubular member 113 is threadedly secured to the upper end of the tubular head 94 and extends upwardly around the conduit 110 through an aperture 114 in the top wall of the vessel 10. Also, a suitable sealing ring 116 is provided in the aperture 114 to sealingly engage the outer surface of the tubular member 113 and prevent a leakage of the corrosive solution 12 through the top of the vessel 10.

In operation of the electrolytic bridge assembly S6, the head 94 is positioned in the frame 8S at such a level that the lower end 42 of the bridge 4d is disposed within the corrosive solution 12 contained within the vessel 10. The electrolyte contained in the conduit and the bridge 49 gradually drips from the tip 42 to maintain electrical connection between the standard electrode and the solution 12 in the same manner as previously described. As the level of the solution 12 varies in the vessel 10, the head 94 is raised or lowered to assure that the ttip 42 is disposed within the solution 12.

It will be apparent that the height of the tubular head 94 and bridge 40 may be controlled by pulling upwardly or lowering these members, or the head 94 may be of such construction that the head will float in the solution 12 at such a depth that the tip 42 will always be disposed within the solution 12. Therefore, the upper end portion of the tubular head 94 may be maintained above the level of the solution 12 in the vessel 1t) and minimize the possibility of the solution 12 leaking into the tubular member 113 and fouling operation of the apparatus. It should again be noted that the various portions of the supporting structure of the weeping glass bridge 4t), such as the frame 88, tubular head 94, extension 102 and tubular member 113 should be constructed out of the same material as the vessel 10 or out of an inert material, such as various plastics, to prevent the formation of a secondary cell in the solution 12.

From the foregoing it will be apparent that the present invention provides an eflicient and economical system for anodically passivating a vessel containing a corrosive solution. The electrolytic bridge of the present invention will maintain intimate communication between a standard electrode and a corrosive solution under all operating conditions, without either affecting the standard electrode or diluting the corrosive solution. Also, the tubular member providing communication for electrolyte from the standard electrode to the corrosive solution will be protected against Violent agitation of the corrosive solution, or inadvertent blows, to provide an electrolytic bridge having a long service life. It will be further apparent that a continuous and eliicient junction will be provided between the electrolyte and the corrosive solution to assure that electrical communication is provided between the solution and the standard electrode. Also, the present electrolytic bridge assembly will remain operative for an extended period of time without the requirement of attention by the operator of a process employing the present invention.

Changes may be made in the combination and arrangement of parts or elements as heretofore set forth in the specification and shown in the drawings, it being understood that changes may be made in the embodiments disclosed without departing from the spirit and scope of the invention as defined in the following claim.

We claim:

In combination with a metallic vessel adapted to contain a corrosive electrolyte, an article of manufacture for protecting the vessel from attack by said corrosive electrolyte comprising:

(a) an inert electrode positioned in said vessel for contact with the corrosive electrolyte;

(b) a source of direct current connected to said inert electrode and vessel to polarize the vessel with respect to the inert electrode;

(c) a reservoir having at least side walls and a bottom;

(d) a non-corrosive electrolyte contained within said reservoir;

(e) means supporting said reservoir on said vessel at a vertically higher level than the top of said vessel;

aia-as (f) means associated with said reservoir for venting the reservoir to the atmosphere;

(g) a standard electrode removably positioned in said reservoir for contact with the non-corrosive electrolyte therein;

(l1) control means connected between said standard electrode and said vessel and responsive to changes in the potential difference between said standard electrode and said vessel for controlling the ow of current between said inert electrode and said vessel; and

(i) an electrolytic bridge between said reservoir and said vessel for placing the removable standard electrode in electrical communication with the corrosive electrolyte in said vessel, said electrolytic bridge comprising:

(1) a weeping glass bridge positioned in said vessel for immersion in the corrosive electrolyte therein, said weeping glass bridge having a restricted opening in the lower end therefor for permitting non-corrosive electrolyte to pass from the weeping glass bridge into the corrosive electrolyte under the influence of hydrostatic pressure;

(2) rigid tubular shield means surrounding said weeping glass bridge and protecting the bridge from mechanical vibration and from agitation of the corrosive electrolyte;

(3) means for mounting the shield means to said vessel; and

D :la

(4) a conduit having one of its ends attached to said weeping glass bridge and the remaining end inserted through the bottom of said reservoir, the terminus of said conduit within said reservoir being positioned at a level suciently high within said reservoir that foreign matter and free crystals of salt will not enter said conduit terminus.

References Cited in the le of this patent UNITED STATES PATENTS 1,779,232 Handforth Oct. 31, 1930 1,944,738 Grebe et al. Ian. 23, 1934 1,951,395 Coons Mar. 20, 1934 2,289,589 Pomeroy July 14, 1943 2,289,610 Wallace Iuly 14, 1943 2,576,680 Guitton Nov. 27, 1951 2,584,816 Sands Feb. 5, 1952 2,759,887 Miles Aug. 21, 1956 2,803,797 Cowles Aug. 20, 1957 2,918,420 Sabins Dec, 22, 1959 FOREIGN PATENTS 551,598 Great Britain Mar. 2, 1943 678,648 Great Britain Sept. 3, 1952 OTHER REFERENCES Edeleann: Metallurgia, September 1954, pages 113-6. Krefeld: German application Serial No. F9115, printed 30 September 15, 1955. 

